1. Field of the Invention
The present invention relates to an induction-heating cooking apparatus wherein loads such as a cooking pan containing food to be cooked are heated, and more particularly to a load applicability detecting device for the induction-heating cooking apparatus.
2. Description of the Prior Art
In conventional induction-heating cooking apparatus, high frequency currents are fed to a heating coil from an inverter so that high frequency magnetic fields are generated around the heating coil, thereby heating a load such as a cooking pan containing food to be cooked. The induction-heating cooking apparatus is provided with a detecting circuit for determining whether or not the load is applicable to the electromagnetic induction-heating so that the cooking pan formed of material unapplicable to the electromagnetic induction-heating or small cooking pans are prevented from being applied unconsciously, or that forks, kitchen and table knives or the like are prevented from being mistakenly heated. Such load applicability detecting circuits are classified into two types. One of the types relies upon an input current to the inverter being approximately proportional to the bottom area of the load. The other type relies upon the input current to the inverter and a high frequency voltage output of the inverter showing different characteristics in accordance with various loads.
In the former type, however, when an output of the inverter is manually set at "LOW" with an inverter output setting means, relatively small cooking pans are not heated when applied. Furthermore, since a detection level of the load applicability detecting circuit is changed in accordance with the inverter output set with the inverter output setting means, a long period of time is required to detect the applicability of the load when the inverter output is set at a high level. Consequently, heat is applied to the small load for a long time, so that the temperature of the load is abnormally increased.
Whereas, in the latter type, the determination is made whether or not the load is too small for induction-heating based on the characteristic that the input current to the inverter is varied with respect to various kinds of loads, though the output voltage of the inverter is maintained at an approximately given value. However, when the value set by the inverter output setting means is small, the input current to the inverter varies little in accordance with various loads. Consequently, detection of the applicability of small loads is difficult.